The present invention relates to the problem of reconstructing structures from X-radiographs in order to obtain, about the interior of a body, a type of information which is not evident in normal radiographs because these present two-dimensional projections of three dimensional objects, and many structural features are superimposed together on the plane of the radiographs.
It is well known that a radiograph is a two dimensional projection of a three dimensional body and many structural features of the body are superimposed onto the radiograph and are difficult to interpret. In order to distinguish superimposed features and reconstruct structures from their projections, different methods and apparatus are currently available. The oldest and most widely used radiological technique is that universally known as tomography, whose early development goes back to the 1920's, e.g. U.S. Pat. No. 3,091,692. One of the more recent developments is disclosed in U.S. Pat. No. 3,778,614, and on its basis there has been commercially produced the EMI scanner for brain research. Another is represented by the commercially available ACTA scanner, referred to in Science, Vol 186 (1974) page 207. Finally, a variety of methods and apparatus have been presented at the first International Workshop on Reconstruction Techniques held at Brookhaven, N.Y. from July 16 to 19, 1974, and are recorded in the Proceedings of that Congress, which have apparently not been published yet. In this specification all of the above methods and apparatus will be referred to as "the methods and apparatus presently available".
A characteristic which is common to all the scanners presently available is the low resolution of the reconstructions, and for this reason, only gross anatomical features can at present be reconstructed, and the interpretation of fine details is often impossible. The low resolution of the present scanners is due both to the limits of the experimental systems of scanning and to those of the mathematical algorithms which are used for computing the reconstructions. The present invention is dedicated to obtain substantial improvements in scanning systems and reconstruction algorithms.